1. a School of Earth and Space Science , Peking University , Beijing , 100871 , PR China
2. b Earth System Science Interdisciplinary Center , University of Maryland , College Park , MD , 20740 , USA
3. c Institute of RS & GIS, Peking University , Beijing , 100871 , PR China
4. d Beijing Key Lab of Spatial Information Integration and its Applications , Peking University , Beijing , 100871 , PR China
5. e NASA Goddard Space Flight Center, Code 618, Biospheric Sciences Laboratory , Greenbelt , MD , 20771 , USA